In particular, in a disc brake, the brake caliper is arranged straddling the outer peripheral edge of a disc brake. The brake caliper usually comprises a body having two elongated elements that are arranged so as to face opposite braking surfaces of the disc. Friction pads are foreseen arranged between each elongated element of the caliper and the braking surfaces of the brake disc. At least one of the elongated elements of the body of the caliper has cylinders suitable for receiving hydraulic pistons capable of exerting a thrusting action on the pads abutting them against the braking surfaces of the disc to exert a braking action on the vehicle.
The brake calipers are usually fixedly connected to a support structure that stays still, with respect to the disc, like for example the forks of a motorcycle or a support fixedly connected to the forks of the motorcycle.
In a typical arrangement, one of the two elongated elements has two or more attachment portions of the body of the caliper to the support structure, for example foreseeing slots or eyelets, for example arranged axially, or tnrough holes, for example arranged radially, suitable for receiving screws for fixing the caliper that, with their ends are received in threaded holes foreseen on the support of the caliper.
In a typical caliper body construction, the elongated elements arranged facing the braking surfaces of the disco are connected together by bridge elements arranged straddling the disc.
The caliper comprises different components mounted on the body such as the pistons, gaskets, drainage devices and brake fluid supply ducts.
Typically, the body of the caliper is made from metal like for example aluminium, aluminium alloy or steel. The body of the caliper can be obtained by fusion, but also by mechanical processing with chip removal, as well as by forging.
The body of the caliper can be produced either in a single piece or in a monoblock, but also in two half-calipers typically connected together along a plane that usually coincides with the middle plane of the disc on which the caliper is arranged to straddle.
In the case in which the driver of the vehicle wishes to brake or slow down the movement of the vehicle, he applies a pressure on the brake pedal, in the case of an automobile, or on the brake lever, in the case of a motorcycle. Such pressure on the brake lever, by means of a brake pump, exerts a pressure in the brake fluid that through a duct is applied to the brake fluid present in the hydraulic circuit placed inside the body of the caliper until it reaches the cylinders where the pressure is exerted on the surface of the bottom of the pistons forcing them to lock against the pads, which in turn abut against the braking surfaces of the disc. The pressure action of the brake fluid is also exerted on the bottom wall of the cylinder determining a reaction in the body of the caliper that deforms it away from the surfaces of the disc. This deformation of the body of the caliper leads to an increase in the stroke of the pistons and thus, to an increase of the stroke of the brake lever.
The body of the caliper must therefore have sufficient structural rigidity, so as to ensure that this deformation of the body of the caliper caused by the braking action is kept within tolerable values, which, as well as avoiding damage to the braking system, do not create the sensation for the driver of an unresponsive braking system, determining an extra stroke of the brake lever (creating a “spongy” sensation). This need pushes towards having extremely rigid structures for the bodies of the calipers and therefore increasing their bulk and weight.
On the other hand, the body of the caliper, being fixedly connected to the suspension of the vehicle and being arranged straddling the disc, is one of the unsuspended masses that it is wished to reduce as much as possible to increase the performance of the vehicle.
Of course, these considerations are taken to the extreme when the vehicle is a racing vehicle and the user wishes to have a braking system that is extremely responsive to his commands and at the same time extremely light so as not to penalise the performance of the racing vehicle.
Therefore, there is a need for a caliper body for a disc brake, which has improved structural characteristics for the same weight of the body of the caliper, or else with the same structural characteristics for a lower weight compared to solutions of the prior art.
Solutions for caliper bodies are known that have been specially studied to increase the characteristics of structural rigidity. For example, patent application EP-A-2022999, patent application EP-A-1534974, U.S. Pat. No. 6,708,802, patent application EP-A-1911989, patent application PCT/EP2005/050615, patent application JP-A-09257063 and patent U.S. Pat. No. 3,183,999 present solutions of bodies for brake calipers equipped with reinforcing elements arranged around Caliper bodies. In some of these known solutions, the caliper body is symmetrical according to planes passing through the axis of the disc or through the middle of the disc. In other solutions the caliper body has large and distributed windows even passing straight through that form elongated reinforcement elements arranged longitudinally to the body of the caliper.
Although satisfactory from many points of view, these known solutions nevertheless do not allow structures to be obtained that maximise the structural rigidity of the body of the caliper reducing the weight and at the same time reduce the bulk as much as possible so as to facilitate the assembly of the body of the caliper even inside wheel rims on which brake discs having a large diameter are mounted.